Various electronic devices provided with a thin display panel such as a liquid crystal display capable of receiving an operational input on its display surface have been proposed. For example, Patent Literature 1 discloses a touch sensor for detecting an operational position, which is disposed on a front face of a display panel. When an operator touches an operation surface, the touch sensor detects a touch position, and the electronic device executes processing according to the detected operational position.
In the case where such conventional electronic device with touch sensor includes a display panel requiring a polarizing plate such as a liquid crystal panel, components constituting the electronic device are disposed as follows.
A front polarizing plate is disposed on the operation surface (outermost face). A touch panel is disposed on the opposite side of the front polarizing plate to the operation surface. A liquid crystal panel formed of a pair of glasses that sandwiches liquid crystal therebetween is disposed on the opposite side of the touch panel to the front polarizing plate. A rear polarizing plate is disposed on the opposite side of the liquid crystal panel to the touch panel. That is, the touch panel is disposed between the front polarizing plate and the rear polarizing plate.
With the above-mentioned structure, in the case of a transmission liquid crystal display, light from a backlight disposed on the rear face of the rear polarizing plate penetrates the rear polarizing plate, the liquid crystal panel, the touch panel, and the front polarizing plate in this order and then, is emitted to the operation surface. In the case of a reflection liquid crystal display, for example, a reflective plate is provided in place of the rear polarizing plate, and light incident from the operation surface penetrates the front polarizing plate, the touch panel, the liquid crystal panel, the reflective plate, the liquid crystal panel, the touch panel, and the front polarizing plate in this order and then, returns to the operation surface.
The front polarizing plate and the rear polarizing plate have the property of transmitting only a wave (light wave) vibrating in a certain direction. The direction in which the wave is transmitted is a polarizing direction. Accordingly, the polarizing direction of the front polarizing plate, the polarizing direction of the rear polarizing plate, and optical characteristics of the liquid crystal panel are combined to set contrast and transmittance of the liquid crystal display and improve appearance of the display screen.
Patent Literature 1—Japanese Patent Unexamined Publication No. 2012-230657 bulletin